Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations supplied, the description carries the full burden and does a decent job: it discloses metered cost (€0.0005 per call), the auth mechanism (API key in Authorization: Bearer), and coverage breadth (501 countries/regions). It does not say what happens on an unsupported country, an out-of-range year, or an ambiguous subdivision code, nor whether failed calls are billed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with purpose before cost/auth, then a structured parameter rundown where each entry is a single clause with no filler. It is dense to the point of being a run-on, and the 'Parameters —' block would read better as separate lines, but nothing is redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return-value explanation is unnecessary, and the remaining gaps for a 7-param, zero-required-argument tool are all covered: operation modes, code formats, date/number formats, cost, and auth. An agent has everything needed to construct a valid call without trial and error.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0% and all seven parameters are typed only as bare strings, so the description is doing the entire documentation job: it gives op values and the default, accepted country code forms (ISO-2/3 or exact code from op=countries), date format YYYY-MM-DD, and days as a signed integer. The subdiv example 'BY for Bavaria' is questionable (Bavaria's ISO-3166-2 code is DE-BY; BY alone reads as Belarus), and op's allowed values are not schema-enforced, which keeps this short of a 5.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The first sentence names the resource (official holidays) with scope (by ISO-3166 country and region) and enumerates the concrete capabilities: localized names, workday check, business-day shift. The parameter block then names four distinct operations (list, is_workday, add_business_days, countries), which makes it unmistakable against siblings like tz_convert or weather.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Guidance is given per-operation by binding parameters to ops: 'year: for op=list (default current year)', 'date: ... for op=is_workday and op=add_business_days', 'days: ... for op=add_business_days'. That is clear context for choosing the right op. It stops short of explicit exclusions or naming an alternative tool when a different one would be better.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.